The OVP mod would probably include cutting one trace. To decrease the 1.3V limit at pin#17 (DIFFOUT), one would have to increase resistance between Vfb (pin#19) and DIFFOUT, in order to decrease the voltage at diffout. Probably not worth the effort as ~1.6V is very high already. I'd rather say that perhaps some other mods. Better filtering VGPU could help get another extra MHz. Sometimes, voltage alone isn't really that helpful.